Weld metal deposits and arc welding electrodes for producing the same



United States Patent 1 2,871,552 WELD METAL DEPOSITS AND ARC WELDING ELECTRODES FOR PRODUCING THE SAME Tore Mans Ivan Norn, Goteborg, Sweden, assignor to Elektriska Svetsningsaktiebolaget, Goteborg, Sweden, a

corporation of Sweden No Drawing. Application March 19, 1956 Serial No. 572,194 Claims priority, application Sweden May 10, 1946 Claims. (Cl. 29-194) This application is in part a continuation of my application Ser. No. 258,293 filed November 26, 1951, now abandoned, said application Ser. No. 258,293 being in part a continuation of my application Ser. No. 744,017 filed April 25, 1947, now abandoned.

This invention relates to weld metal deposits suitable for constituting hard facings on metallic articles as well as to arc welding electrodes for producing such deposits or facings.

It is an object of the invention to produce a weld metal deposit which can be worked with cutting tools in the aswelded state without any special pretreatment, and which can be caused to assume a high degree of hardness and wear resistance through a simple subsequent heat treating process. It is a further object of the invention to provide an improved arc welding electrode for producing a deposit of the type indicated. Other objects of the invention will be clear from the following specification.

According to a principal feature of the invention, the improved-weld metal deposit consists of a precipitation hardening, substantially carbon free alloy of the type Fe-Co-M, in which M signifies metal from the group consisting of tungsten, molybdenum, niobium and tantalum, the cobalt content. of said alloy being not less than 3% by weight and not more than the amount Co indicated by the formula in which the chemical signs W, Mo, Nb and Ta represent the individual percentages by weight of the respective metals in the aloy, the content of metal selected from the group consisting of tungsten, molybdenum, niobium and tantalum being not less than 4% by Weight and not more than consistent with the formula in which the chemical signs W, Mo, Nb and Ta represent the individual percentages by weight of the respective metals in the alloy, the aggregate content of cobalt and metal of the group comprising tungsten, molybdenum, niobium and tantalum not exceeding 95%, the balance of the alloy being principally iron.

While carbon will practically always be present as an impurity, it is important that the content of carbon be kept as low as possible so as not to increase the hardness of the deposit in the as-Welded condition. The carbon content must in no case exceed 0.3% and should preferably be kept below 0.1%. Other usual impurities are manganese and silicon, the aggregate content of which should not exceed 1% or at most 1.5%. Sulphur and phosphorus will cause no trouble in the low contents usual in weld metal deposits.

The invention also comprises an arc welding electrode adapted to produce a weld metal deposit of the kind above indicated. The arc welding electrode according to the invention consists of a metallic core and a coatingconsisting substantially of flux-forming substances, metallic substances and a binder, and the electrode is particularly characterized thereby that the metallic portion constituted ice by said core and said metallic substances consists substantially of cobalt, iron and at least one metal of the group consisting of tungsten, molybdenum, niobium and tantalum, the cobalt content of said metallic portion being not less than 3% by weight and not more than the amount Co indicated by the formula 40W+3'Mo+25Nbl-25Ta 0 W+Mo+Nb+Ta 0 in which formula the chemical signs W, Mo, Nb and Ta represent the individual percentages of the respective metals by weight of said metallic portion, the content of metal selected from the group consisting of tungsten, molybdenum, niobium and tantalum being not less than 4% by weight and not more than consistent with the formula in Which the chemical signs W, Mo, Nb and Ta represent the individual percentages by weight of said metallic portion, the aggregate content of cobalt and metal from the group indicated not exceeding 93% by weight of said metallic portion, the remainder of said metallic portion being principally iron. Deoxidants, as manganese and silicon, usually in the form of ferroalloys, may be present in the quantities usual in arc welding electrodes. At it is desired to obtain a weld metal of low carbon content, the carbon contents of the various metallic constituents of the welding electrode should be low.

The weld metals according to the present invention may be either ferritic, semi-ferritic, martensic or austenitic. For information concerning the .metallography of these alloys, reference may be made to Archiv fiir das Eisenhiittenwesen 1931/32, page 431; the same 1932/33, page 17; and the same 1939/ 40, page 93, as well as to Houdremont: Handbuch der Sonderstahlkunde, Berlin 1943, pp. 726 ff.

The ternary alloys which are to be preferred according to the invention are tabulated here below:

TABLE Composition preferred according to the invention for welding deposits consisting of ternary alloys of the type Fe-Co-M.

Generally with- Preferably Particularly within the within the within the limits limits limits Type Percent Percent Percent Percent Percent Percent 00 W 00 W 00 W 3-60 4-40 3-12 12-30 9-12 12-15 ferrltic.

20-40 6-20 26-32 10-16 martensitic.

23-30 43-44 28-30 semi-terrific. 40-50 30-40 40-43 36-39 anstenitic.

Percent Percent Percent Percent Percent Percent 00 Mo 00 Me 00 Mo 3-18 10-30 8-12 15-18 ferritic.

. 25-38 5-15 28-30 8-12 martensitic.

. 37-40 15-20 39-40 15-17 semi-ferritic.

45-65 15-30 48-52 20-23 austenittc.

Percent Percent Percent Percent Percent Percent 00 Ta or 00 Ta or 00 Ta or 5-15 12-20 9-11 15-17 ierritie.

. 25-50 8-20 46-50 8-14 martensittc.

. 68-70 12-14 68-70 12-14 somi-ferritic.

. 68-72 17-23 69-70 19-21 austenitic.

It should be understood that the invention is not limited to welding rods yielding a welding deposit consisting of ternary alloys, but also comprises rods the welding deposit of which contains two or more of the metals tungsten, molybdenum, niobium and tantalum.

The alloying elements of cobalt and one or more elements from the group comprising tungsten, molybdenum, niobium and tantalum, may be present in the welding rod of the present invention either in their elemental form or in the form of compounds. For instance, the welding rods may comprise a wire having substan tially the same composition as the alloy to be deposited, with a fluxing coating of suitable composition, or they may consist of a metallic core provided with a coating containing additional metals or reducible metal compounds in such amounts that the alloy resulting from blending under welding conditions of the fused metals of the core with the fused metallic constituents of the coating or with the metals reduced out of the reducible metal compounds will have compositions as defined by the present invention.

The principal advantage of the welding rods of the present invention is that the weld metal obtained after rapid cooling from high temperatures, e. g. l200-1300 C., which are normal welding temperatures, can be worked with cutting tools. The present invention provides directly machinable welds which can subsequently be hardened to hardnesses equal to or even surpassing those of the hard metals simply by annealing the welds to temperatures suited to the composition of the alloy in the range of from 500 to 700 C. This annealing also has the additional advantage of removing a martensitic zone that may incidentally be present in the base material.

Annealing of the metal weld of the present invention can be done by local heating, as with a carbon are or by furnace heating when relatively small pieces are involved. Furnace heating gives the best results and is to be preferred where practicable. Different degrees of hardness can be obtained by varying the annealing temperatures and also by controlling the welding conditions, particularly the temperature of the work piece during welding.

Crack-proofness of the welds of the present invention is good since no hardening in the ordinary sense of the term occurs in the weld metal during welding (or during subsequent treatment). The weldability of the welding materials of the present invention is very good since the deposited alloys are almost completely free from carbon. Absence of carbon also minimizes the danger of forming pores and cracks in the Welding.

The weld rods of the present invention are therefore very suitable for veneering wearing surfaces and the like, for the manufacture and repair of cutting tools, for the hard facing of rolling mill rolls, and the like.

The following table contains three examples of suitable coating mixtures for electrodes according to the invention having a core of iron or mild steel:

Each of the above coating compositions was mixed with a solution of potassium silicate to a paste-like consistency and extruded on 3.25 mm. core wires of mild steel (C=0.07), the diameters of the coating being 7.8 mm. for Examples I and II, and 6.8 mm. for Example III. The ratio of the weight of the dried coating to the eight of the core wire amounted to 1.99, 2.03, and 1.35 for Examples I to III, respectively. The compositions of the undiluted weld deposits obtained under normal welding remainder iron with insignificant amounts of Mn (0.5 to 0.7%), Si (about 0.04%), P and S (less than 0.02% each).

The above compositions I and II are of the martensitic type, while composition No. III belongs to the ferritic type.

According to another example, the coating is composed of the following mixture.

n EXAMPLE 1v Percent Ferro-silicon (50%) 2 Perm-manganese (80%) 2 Ferro-molybdenum (70%) Non-metallic flux 66 The non-metallic flux may have the same composition as stated in connection with Examples I to III. The coating composition is mixed with a solution of potassium silicate and extruded on core wires of an iron-cobalt alloy containing 50% of each metal, the extruding diameter being such as to result in a ratio of about 1.08 between the weight of the dried coating and the weight of the core. The electrode thus manufactured will yield on welding under normal conditions (positive polarity, 125 amps in the case of a 3.25 mm. electrode) a weld deposit having the following composition (undiluted):

Percent about 0.07 Mo bout-.. 17.2 C0 a out" 38.5 Remainder iron with insignificant amounts of Mn and Si.

This alloy is of the semi-ferritic type.

In the Examples I to IV, all or a substantial part of the alloying additions are supplied by the coating. In the following Examples V to XVI, the electrode consists of a core containing all of the alloying additions required, while the coating consists of fluxing substances and deoxidants only.

Example I II III Composition of core Percent Percent Percent yp of weld Ferro-silicon 50%) 2 2 3 Example deposit Farm-manganese (80%)...- 2 2 2 Ferro-tungsten (80%) g Percent Percent Percent Percent Ferro-molybdenurn 22 Ferro-columbium (65%) 44 Cobalt 35 35 16 ferritlc. Non-metallic flux 42 39 35 t csemi-terrific. austenitlc. ferritic. The non-metallic flux may, for lnstance, be cornmartensitic. osed of semi-ferrltic. p austenittc Percent ferrigie. m mar ens c Llmestone 53 70 10 semt-ferrltlc. Fluorspar 36 70 25 austenltlc. Rutile 11 An example of a coating composition suitable for the above core compositions is:

Percent Ferro-silicon (50%) 2 Ferro-manganese (80%) 2 Limestone 5 1 Fluorspar 35 Rutile Percent W 13 Co 12 Remainder iron with insignificant amounts of silicon, manganese, and carbon.

It will be noted that said percentages of W and Co are within the narrow limits indicated in the last column of the first table of the present specification. Similarly, the cores VI to XVI when provided with a coating of the type above indicated will yield weld deposits of the kind indicated in said column.

The invention is not restricted to the above examples, but comprises all embodiments within the scope of the appended claims.

I claim:

1. A metal article having a metal deposit welded thereto, said deposit comprising a precipitation hardening, substantially carbon free alloy of the type Fe-Co-M, in which M signifies metal from the group consisting of tungsten, molybdenum, tantalum and niobium, the cobalt content of said alloy being not less than 3% by weight and not more than the amount Co indicated by the formula in which formula the chemical signs W, Mo, Nb and Ta represent the individual percentages by weight of the respective metals in the alloy, the content of metal selected from the group consisting of tungsten, molybdenum, tantalum and niobium being not less than 4% by weight and not more than consistent with the formula in which the chemical signs W, Mo, Nb and Ta represent the individual percentages by weight of the respective metals in thealloy, the aggregate content of cobalt and of the group comprising tungsten, molybdenum, niobium and tantalum not exceeding 95%, the balance of the alloy being principally iron.

2. An arc welding electrode consisting of a metallic core and a coating consisting substantially of flux-torming substances, metallic substances, and a binder, characterized in that the metallic portion constituted by said core and said metallic substances consists substantially of cobalt, iron and at least one metal of the group consisting of tungsten, molybdenum, niobium and tantalum, the cobalt content of said metallic portion being not less than 3% by weight of said portion and not more than the amount Co indicated by the formula in which formula the chemical signs W, Mo, Nb and Ta represent the individual percentages of the respective metals by weight of said metallic portion, the content of metal selected from the group consisting of tungsten, molybdenum, niobium and tantalum being not less than 4% by weight and not more than consistent with the formula in which the chemical signs W, Mo, Nb and Ta represent the individual percentages by weight of said metallic portion, the aggregate content of cobalt and metal from the group consisting of tungsten, molybdenum, niobium and tantalum not exceeding 93% by weight of said metallic portion, the remainder of said metallic portion being principally iron.

3. A metal article having a metal deposit welded thereto, said deposit comprising an alloy comprising 3 to 60% cobalt, 4 to 40% tungsten, the aggregate content of cobalt and tungsten not exceeding 95%, the balance being iron with incidental impurities.

4. A metal article having a metal deposit welded thereto, said deposite comprising an alloy composed of 3 to 65% cobalt, 4 to 35% molybdenum, the aggregate con tent of cobalt and molybdenum not exceeding 95%, the balance being iron with incidental impurities.

5. A metal article having a metal deposit welded thereto, said deposit comprising an alloy composed of 3 to cobalt, 4 to 25% niobium, the aggregate content of cobalt and niobium not exceeding the balance being iron with incidental impurities.

6. A metal article having a metal deposit welded thereto, said deposit comprising an alloy composed of 3 to 75% cobalt, 4 to 25% tantalum, the aggregate content of cobalt and tantalum not exceeding 95%, the balance being iron with incidental impurities.

7. An arc welding electrode consisting of a metallic core and a coating consisting substantially of flux-forming substances, metallic substances, and a binder, charac terized in that the metallic portion constituted by said core and said metallic substances contains 3 to 60% cobalt and 4 to 40% tungsten, the aggregate content of cobalt and tungsten not exceeding 93% by weight of said metallic portion, the balance of said metallic portion being iron with incidental impurities.

8. An arc welding electrode consisting of a metallic core and a coating consisting substantially of flux-forming substances, metallic substances, and a binder, characterized in that the metallic portion constituted by said core and said metallic substances contains 3 to 65 c0- balt and 4 to 35% molybdenum, the aggregate content of cobalt and molybdenum not exceeding 93% by Weight of said metallic portion, the balance of said metallic portion being iron with incidental impurities.

9. An arc welding electrode consisting of a metallic core and a coating consisting substantially of flux-forming substances, metallic substances, and a binder, characterized in that the metallic portion constituted by said core and said metallic substances contains 3 to 75% cobalt and 4 to 25 niobium, the aggregate content of cobalt and niobium not exceeding 93% by weight of said metallic portion, the balance of said metallic portion being iron with incidental impurities.

10. An arc welding electrode consisting of a metallic core and a coating consisting substantially of flux-forming substances, metallic substances, and a binder, characterized in that the metallic portion constituted by said core and said metallic substances contains 3 to 75% cobalt and 4 to 25 tantalum the aggregate content of cobalt and tantalum not exceeding 93% by weight of said metallic portion, the balance of said metallic portion being iron with incidental impurities.

References Cited in the file of this patent UNITED STATES PATENTS Wissler Apr. 18, 1933 Stoody et a1. May 30, 1939 Wlssler Oct. 29, 1940 Franks July 4, 1950 UNITED STATES PATENT OFFICE Certificate of Correction Patent No. 2,871,552

of the formula, for +3 the table, heading to columns 1 and column 4, line 6, for eight read Weight Tore Mans Ivan Norn February 3, 1959 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below. Column 1, line 43, for aloy read alloy; column 2, line 7, indistinct portion as shown below instead of as in the patent line 24, for deposite read -=deposit-.

Signed and sealed this 26th day of May 1959.

[SEAL] Attesfi: KARL H. AXLINE, Attestz'ng Oficer.

read --+35; line 26, for At read As; line 47, in tlm-eof, after Generally strike out with; column 6, lines 8 to 10 should appear ROBERT C. WATSON, flommz'ssz'oner of Patents.

I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noe 2,871,552 February 3 1959 t3 Tore Mans Ivan Noren It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2;, line 31, for "martensio" read an martensitic ""v (SEAL) Attest:

KARL H, I ROBERT C. WATSON Attesting Oflicer Commissioner of Patents UNITED STATES PATENT OFFICE Certificate of Correction Patent N 0. 2,871,552 February 3, 1959 Tore Mans Ivan Norn It is hereby certified that error appears in the printed specification of the above numbered atent requiring correction and that the said Letters Patent should read as correcte below.

Column 1, line 43, for alo read -a.lloy; column 2, line 7, indistinct portion of the formula, for +3 rea +35-; line 26, for At read -As; line 47, in the table, heading to columns 1 and 2 thereof, after Generally strike out with-; column 4, line 6 for eight read -weight; column 6, lines 8 to 10 should appear as shown below instead of as in the patentline 24, for deposite read deposit.

Signed and sealed this 26th day of May 1959.

[SEAL] Attest= KARL H. AXLINE, ROBERT C. WATSON, Atteetz'ng Oficer. aommiaszmr of Patents.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,871,552

February 3 1959 Tore Mans Ivan Norn It is hereby certified that error appears in the printed specification of the above numbered patent requir ing correction and that the said Letters Patent should read as corrected below.

Column 2, line 31, for "martensic" read martensitic Signed and sealed this 28th day of July 1959.

SEAL) ttest:

KARL H AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents 

1. A METAL ARTICLE HAVING A METAL DEPOSIT WELDED THERETO, SAID DEPOSIT COMPRISING A PRECIPITATION HARDENING, SUBSTANTIALLY CARBON FREE ALLOY OF THE TYPE FE-CO-M, IN WHICH M SIGNIFIES METAL FROM THE GROUP CONSISTING OF TUNGSTEN, MOLYBDENUM, TANTALUM AND NIOBIUM, THE COBALT CONTENT OF SAID ALLOY BEING NOT LESS THAN 3% BY WEIGHT AND NOT MORE THAN THE AMOUNT COMAX INDICATED BY THE FORMULA 